1. Field of the Invention
The invention relates to a hanger and hanger mount assembly for a chest drainage unit and relates more specifically to a hanger and hanger mount assembly for a chest drainage unit that is adjustable to allow the chest drainage unit to hang in a vertical direction even when the chest drainage unit is displaced from its free hanging vertical position.
2. Description of Related Art
Chest drainage units (CDUs) are used to collect and measure fluids and other material from a patient's chest during and after surgery and as a result of injury to the patient's chest. It is important to accurately measure the amount of fluids and other material collected in the CDU from the patient in order to adequately monitor the patient's condition and be alerted to problems that may be developing.
CDUs typically have indicia to visually indicate the amount of fluids and other material removed from the patient's chest during use. These indicia usually takes the form of markings on the outside of the CDU corresponding to certain volumes of fluid and other material collected inside the CDU.
To determine the volume of fluids or other material collected, the series of indicia are usually visually aligned with the top surface of fluids and other material collected in the CDU. The specific indicia aligned with this top surface corresponds to the volume of such material collected in the CDU.
In the system of determining the volume of material collected in a CDU described above, the indicia correspond to volumes of material in the CDU when the CDU is in its most vertical position. Any deviation of the CDU from its most vertical position causes a misalignment of the top surface of the material collected and the correct indicia corresponding to the actual volume. In fact, when the CDU is moved sufficiently from its most vertical position, the top surface of the material collected will be aligned with an indicia corresponding to other than the correct volume of material collected so that an incorrect reading of the amount of material collected is obtained.
During use, many chest drainage units (CDUs) are suspended by a pair of hangers from a rail that is part of the bedframe. Referring to FIGS. 1 and 2, the CDU is generally labeled 2. The CDU 2 has a top 4, a front 6, a back 8 and a pair of opposed sides 10. Top sides 12 are formed where top 4 intersects opposed side 10.
A rigid hanger 14 connects CDU 2 to a bedframe piece 16 or similar support. Usually, a pair of hangers 14 connect CDU 2 to bedframe piece 16 from opposite ends of the top 4 of CDU 2 at a mount 18 as shown in FIG. 2. FIG. 1 shows only one hanger 14, the other hanger 14 being a mirror image of the hanger 14 shown.
Hanger 14 has a curved end 20 that extends around bedframe piece 16 and a pivot end 22 that is pivotally attached to the CDU 2 at mount 18. Mount 18 is attached to the top 4 of CDU 2 between CDU front 6 and CDU back 8 so that when curved end 20 is placed over bedframe piece 16 and CDU 2 is allowed to freely hang, pivot end 22 is directly above the horizontal line extending through the center of gravity of the CDU 2 that intersects the opposed sides 10 of CDU 2 when CDU front 6 and CDU back 8 are both vertical. The point of intersection of the horizontal line extending through the center of gravity of the CDU 2 and the opposed sides 10 of CDU 2 when CDU front 6 and CDU back 8 are both vertical will be referred to throughout this description as intersection point 24. In this way, when the hangers 14 are attached to the bedframe piece 16 and the CDU 2 is allowed to hang freely, CDU 2 hangs from the hanger mount 18 in its most vertical position.
Indicia 26 are typically located on the CDU front 6. This allows the volume of material collected from the patient to be visually determined as described above.
As stated above, the system for hanging CDUs from a bedside anticipates that the CDU will be allowed to freely hang in its most vertical position from a hanger attached to a rail that is part of a bedframe. In actual use several factors occur that prevent the CDU from hanging in its most vertical position.
One of the most common of these situations is shown in FIG. 3. In FIG. 3, the CDU 2 is moved away from its freely hanging vertical position by contact with an object A such as a part of the bedframe. In this common situation, the connection of mount 18 and the pivot end 22 of hanger 14 is constrained to move on an arc B defined by the rotation of hanger 14 around bedframe piece 16 in response to the contact with the object A.
In most CDUs, the length of hanger 14 is relatively short, typically about 4 inches. Because of this relatively short distance, if the object A moves the CDU 2 away from its most vertical position by more than the length of hanger 14, despite the movement of mount 18 and pivot end 22 on arc B, CDU 2 will necessarily be tilted at an angle from vertical. As previously mentioned, any deviation of CDU 2 from vertical results in a misalignment of the indicia 26 with the top of the material collected in CDU 2 so that an accurate reading of the collected amount is difficult or impossible to obtain.
Further, as shown in FIG. 4, even if CDU 2 is displaced away from its most vertical position by less than the length of hanger 14, CDU 2 may still be tilted away from a vertical position by contact between CDU 2 and the contacting object A. Contact between object A and CDU 2 will cause CDU 2 to move horizontally away from its free hanging position. As CDU 2 begins to move horizontally, the contact point between mount 18 and pivot end 22 is constrained to move along arc B. However, this path along arc B causes the center of gravity of CDU 2 to be raised, thus increasing the potential energy of the CDU/hanger system.
Further, because the CDU 2 pivots around the connection between mount 18 and pivot end 22, CDU 2 is a physical pendulum pivoting around the connecting point between mount 18 and pivot end 22. Contact between object A and CDU 2 may also cause this physical pendulum to rotate out of its vertical or lowest energy position to a non-vertical and higher energy position.
Of course, CDU 2 will try to minimize its potential energy by mount 18 and pivot end 22 moving along arc B and also by CDU 2 rotating around the connection between mount 18 and pivot end 22 to minimize the potential energy of the physical pendulum formed by CDU 2. However, frictional contact between CDU 2 and the contacting object A prevents CDU 2 from sliding along the contacting object A as mount 18 and pivot end 22 move along arc B and CDU 2 rotates around the connection point between mount 18 and pivot end 22 to the point of lowest potential energy. Consequently, even slight movement of CDU 2 from its free hanging vertical position may cause CDU 2 to not be vertical thereby making it difficult or impossible to accurately ascertain the volume of material collected in the CDU.
In view of the foregoing, it is desirable to have a hanger mount that allows the alignment of the indicia on the CDU with the top surface of the material collected in the CDU to accurately represent the volume of material collected even if the CDU is displaced from its free hanging vertical position.